How can i make transparent glass like material to put it over another object?
What you need to change is the Saturation and the Value of the Glass BSDF node. With an RGB Input you just do this:



With an image texture, you will need to do something more like this: 



This will make the saturation less, the value less, and the contrast less, allowing the glass to be much more transparent.

Here are some examples:

High Saturation, low Value:



Low Saturation, high Value:



As you can see, the cubes in the background are now visible, and the environment texture behind the sphere is now much more visible.

Other things to check:


The Roughness value
Any mix nodes, even unused (press M to mute them)
The right material is assigned to the object